The present invention relates to a hinge for wings or doors.
In particular, the present invention relates to a hinge which can be used for constraining the doors of electrical appliances, such as ovens, to the respective supporting structures.
In the following description and by way of example only, without limiting the scope of the invention, the present invention is described with reference to an oven.
Hinges of this type normally consist of two separate parts, kinematically connected to one another, directly or by inserting a lever between them.
More precisely, the first of said parts is fixed to the oven structure at one side of the oven mouth, whilst the second part is fixed to one edge of the door, which in that way is rendered movable, with a tilting action, relative to the above-mentioned oven mouth.
One or more elastic elements are inserted between the two parts of the hinge.
During door rotation starting from its closed position, the elastic elements oppose, during a first step, the detachment of the door from the oven supporting frame and, in a second step, they oppose the subsequent rotation of the door and its consequent lowering to an end of stroke position in which the oven mouth is completely open.
In this second opening step, the door, under the combined action of its own weight which promotes its descent and of the elastic elements which apply a braking action, performs a gradual rotation.
During door rotation starting from its open end of stroke position, the action of the elastic elements is first balanced by the weight of the door, initially guaranteeing gradual closing rotation; however, then, in the absence of a braking action by the user, the elastic elements push the door towards the oven frame with sufficient force to guarantee its effective closing.
Basically, the presence of the hinges with elastic elements balances the door, so that when it is opened it does not drop open, and when it is closed it does not forcefully spring back to its closed position.
In its opening and closing movements, irrespective of the action of the user, the door is subject to the action of two different torques, an “opening” torque to which the weight of the door contributes, and a “closing” torque, basically determined by the elastic reaction force of the hinge springs.
At least beyond a predetermined door opening angle, for example greater than 30°, the opening torque will advantageously be positive, whilst the closing torque will have a negative value.
Said values are the preferred values for good operation of the door. If the spring or springs contained in the hinge were too weak, the opening torque could become negative, requiring that the operator apply a braking action to door opening, otherwise the door would just drop open. In contrast, if the spring or springs were to generate an elastic reaction force that was too great, the closing torque could become positive, therefore resulting in violent door closing.
As already indicated, correct door operation basically requires that, at least beyond a predetermined opening angle, the opening torque is positive and the closing torque is negative.
The difference in the absolute value between the two torques in practice indicates the versatility of the hinge, that is to say, the range of different door weights that a predetermined hinge can balance.
Prior art hinges have the disadvantage of being suitable for balancing doors within a rather limited weight range, therefore obliging manufacturers and users to adopt extensive ranges of hinges in order to be able to vary the weights of the doors.
For example, the same electrical appliance, finished with covering surfaces which have different weights, must be fitted with different hinges. This means that in the worst case the hinges and door must be mounted only after the covering has been selected.